Recreating a sense of self is an infinitely confusing goal
Our minds are many things, but they are not pure products of computation. What we consider our sense of self is as much mediated by our personal history and experiences and our interaction with others as it is by the raw grey matter of the brain. And mind is not what it seems -- we think we live in the present, where we perceive events and have thoughts in real time.
We don't -- we live about half a second in the past. Brain scans show that is how long it takes for a perception to become fully integrated with our awareness. Yet we can catch a cricket ball, drive a car and communicate with each other much more quickly than that -- all aspects of being that are in some way removed from our immediate awareness while seemingly part of it.
And the human brain, despite having many similarities to a computer, is unthinkably complex. Each of the neurons in the brain can have up to a thousand connections. When a certain set of conditions at those connections is met, the neuron fires -- but those conditions can vary from moment to moment, depending on what happened last, what state the neuron's in, what the conditions around it are. That's a very large number of variables to take into account, which the neuron does up to a thousand times a second -- and there are 100 billion neurons in the human brain. That's up to 100 trillion synapses, each of which would have to be modelled in a replica system.
Enormous numbers, even if researchers such as Hans Moravec of Carnegie Mellon University think that we'll achieve the necessary 100 million MIPS/100 million MB machines in twenty to thirty years' time. He points out that the human brain has many more neurons than it does bits of DNA -- in other words, the neurons are put together according to a coded scheme, rather than individually, and that much of the creation of mind probably happens after birth. Our machines, should we build them, may programme themselves as babies do.
